1. Field of the Invention
The present invention relates to a cylinder locking device for locking the piston rod of a hydraulic cylinder to stop it in a desired position and, more particularly, to a cylinder locking device which can ensure the locking operation of the piston rod with neither deformation nor wear of the piston rod.
2. Description of the Prior Art
In the prior art, a collet chuck or a hydraulic locking device has been used as the cylinder locking device for locking and stopping the piston rod of hydraulic cylinder. However, either of these has defects such as having a short lifetime and having a structure that is so complicated that production cost is high.
Thus, there has been proposed a cylinder locking device which has a relatively simple structure, as shown in FIGS. 1 and 2. This device is constructed such that a cylindrical housing 2 is fixed eccentrically to a piston rod 3 on the front end portion of a cylinder body 1. A brake disk 4 is fitted rotatably in the housing 2. The piston rod 3 is inserted into an eccentric hole which is formed axially in the brake disk 4. A lever 6 is fixed to an outer circumferential portion of the brake disk 4 and protrudes out through an opening 5 which is formed in a portion of the housing 2. When the lever 6 is pushed down in the direction of the arrow in FIG. 2 to slightly turn the brake disk 4, the brake disk 4 pushes and locks the piston rod 3. At this time, as shown in FIG. 1, the pushing force F caused by the slight turn of the brake disk 4 is applied upward to the lower portion of the piston rod 3 so that it is received only by the upper portions of bearing metals 7 and so that the turning force by the lever 6 is applied to the piston rod 3. As a result, the piston rod 3 is subjected, when it is to be locked, to both shearing forces by the pushing force F and drags F.sub.1 and F.sub.2 generated at the bearing metals 7 and a torsion by the turn. A problem arises because the piston rod 3 and the bearing metals 7 become worn and deformed.